Gas turbine and sealing means for a gas turbine

ABSTRACT

A gas turbine, with a fixed inner housing, arranged concentric to the rotor, with a through flow of working medium, is disclosed. The housing comprises at least two serial rings with an annular gap left between two directly adjacent rings, whereby an annular sealing means is arranged in at least one peripheral groove for sealing the annual gap. According to the invention, a sealing means is provided which permits a greater movement of both components forming the gap, whereby the annual gap is formed by partly overlapping rings, running against the flow direction of the working fluid in the radial sense and the front most of the two rings, in the sense of the flow direction, comprises a locating annular surface for the sealing means embodied as an annular spring element on which the spring element rests under tension such as to seal the annular gap.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International ApplicationNo. PCT/EP2004/009964, filed Sep. 7, 2004 and claims the benefitthereof. The International Application claims the benefits of EuropeanPatent application No. 03020720.3 filed Sep. 11, 2003. All of theapplications are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The invention relates to a gas turbine with a rotationally fixed innercasing which is arranged concentrically with respect to the rotor,according to the claims, and to an annular sealing means for a gasturbine, according to the claims.

BACKGROUND OF THE INVENTION

Such a gas turbine is known from EP 1 118 806 A1. A freely projectingflexural extension is provided for sealing off a gap delimited by twopartially overlapping wall segments. Under thermal action, the flexuralextension flexes in such a way that it closes the gap.

EP 896 128 discloses a sealing element for a gas turbine. The gasturbine has a guide blade ring consisting of adjacent turbine guideblades which form an annular hot-gas duct. Platforms are arranged on theturbine blades for the inner and outer delimitation of the hot-gas duct.Directly adjacent platforms form, with their end faces lying against oneanother, a gap which is sealed off by means of a sealing element. Forthis purpose, a groove is introduced in each case in each end face, saidgrooves lying opposite one another and the sealing element beinginserted into them. The sealing element, of C-shaped cross section,projects in each case with one of the two bent ends into a groove insuch a way that the two arms of the sealing element which extendtransversely with respect to the groove bottom bear in each case againsta flank of the groove and thus seal off the gap between the two adjacentplatforms. The working fluid flowing in the hot-gas duct is thusprevented from leaving the duct through the gap.

Furthermore, a sealing element is known from DE 100 44 848, which sealsoff a gap formed between two static turbine parts. The sealing elementis likewise inserted in two grooves lying opposite one another, but, incontrast to EP 896 128, has a different geometry. The action andfunction of this sealing element are identical to those of theabovementioned sealing element.

When the gas turbine is in operation, thermal expansions arise on thecomponents acted upon by hot gas, such as the guide blades and theirplatforms, and may lead to a displacement of the components with respectto one another.

In the case of a shear displacement directed parallel to the gap, theknown sealing elements allow only relatively small displacement travel.

SUMMARY OF THE INVENTION

The object of the invention is, therefore, to specify a sealing meansfor a gas turbine, which is effective even in the case of greaterdisplacement travel. The object is, furthermore to specify a gas turbineappropriate for this purpose.

The object is achieved, with respect to the gas turbine, by means of thefeatures of the claims and, with respect to the sealing means, by meansof the features of the claims.

The solution for achieving the object proposes, with respect to the gasturbine, that the sealing means be designed as a spring element with afirst end, with a second end and with a spring region lying betweenthem, and that the first end be secured in one of the two rings in acircumferential groove open toward the annular gap, and that the collararranged on the other of the two rings have, for the second end of thespring element, an annular bearing surface, against which the springelement bears, prestressed, so as to seal off the annular gap, while, inorder to generate the prestress, the spring region is supported on anannular supporting surface which is provided on the collar of the onering and which faces the annular bearing surface.

When the gas turbine is in operation, the two rings move in relation toone another on account of thermal expansions. These movements areparallel to the annular bearing surface, perpendicular thereto or amixture of the two movements. In this case, the spring prestress causesthe automatic follow-up of the spring element on the annular bearingsurface, without the spring element losing contact with the annularbearing surface and the spring element thus losing the sealing action.Only the contact line is displaced in the axial direction along theannular bearing surface.

In order to generate the spring prestress, the spring element utilizesas an abutment an annular supporting surface which is arranged on theinside, facing the hot-gas duct, of the outer collar. In this case, thespring element bears at least partially between its two ends against theabutment. The sealing action can be maintained, since, as a result ofthe support of the spring element, the free or second end can followespecially high radial displacements, that is to say, even when the gapdimension increases appreciably, the sealing action remains maintained.

Since the spring element has an elongate configuration in cross section,a greater shear displacement, that is to say in the radial directionwith respect to the rotor, of the two components in relation to oneanother is possible.

Advantageous embodiments are specified in the subclaims.

Expediently, the inner casing is designed to diverge conically towardthe rotor in the flow direction.

A simple overlapping of the collars arranged on the adjacent rings andextending in the direction of divergence is afforded when the frontwing, as seen in the flow direction, has the radially inner collar andthe rear ring has the outer collar, so that, as seen radially, theannular gap runs counter to the flow direction of the working fluid.This arrangement impedes the deeper inflow of the hot gas into the gapto be sealed off, since the hot gas loses kinetic energy duringpenetration as a result of the reversal in flow direction brought aboutby a bend at right angles. The spring element is thus acted upon by thehot gas solely by a lower radially outward-directed force than thespring prestress.

For this purpose, the fixed end of the spring element is introduced asfixed bearing in a circumferential groove provided on the end face ofthe rear ring and can be connected, gas-tight, to the rear ring bywelding or soldering. During movements, therefore, the spring elementalways co-moves in synchronism with the rear ring.

In a further embodiment, the annular bearing surface is provided on thatside of the radially inner collar which faces away from the workingfluid and therefore on the front ring. The spring element, of S-shapedcross section, can then bear sealingly as a free bearing with its freeend against the annular bearing surface.

Especially advantageous is the embodiment in which, outside the innercasing, a cooling medium can flow, the pressure of said cooling mediumbeing higher than the pressure of the working fluid inside the innercasing, and in which the spring action of the sealing means runs in thedirection of the pressure drop. As a result, the spring action of thespring element is assisted by the appreciable pressure drop between thecooling medium and working fluid. The additional pressure force thusgenerated is dependent on the area of the spring element on which thecooling medium can act and becomes higher with a rising pressuredifference. The additional pressure force leads to an improved sealingaction. Even in the event that the spring prestress diminishes, areliable bearing of the free end of the spring element against theannular bearing surface is thus ensured during operation.

The solution for achieving the object proposes, with respect to thesealing means for a gas turbine, which seals off a gap delimited by twodirectly adjacent components which in each case have a collar in theregion of the gap and therefore partially overlap one another, that thesealing means be designed as a spring element with a first end, with asecond end and with a spring region lying between them, and that thefirst end be secured in one of the two components in a groove opentoward the gap, and that the collar arranged on the other of the twocomponents have, for the second end of the spring element, a bearingsurface against which the spring element bears, prestressed, so as toseal off the gap, while, in order to generate the prestress, the springregion is supported on a supporting surface which is provided on thecollar of the one component and which faces the bearing surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described with regard to the gas turbine in this casealso apply accordingly to the sealing means.

The invention is explained by means of drawings in which:

FIG. 1 shows an annular gap with a sealing means,

FIG. 2 shows a part longitudinal section through a gas turbine, and

FIG. 3 shows the annular gap according to FIG. 1 with offset rings,

FIG. 4 shows the annular gap according to FIG. 3 after calking of thecircumferential groove.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2 shows a gas turbine 1 in a part longitudinal section. It has,inside it, a rotor 3 which is rotationally mounted about an axis ofrotation 2 and which is also designated as a turbine rotor or rotorshaft. An intake casing 4, a compressor 5, a toroidal annular combustionchamber 6 with a plurality of coaxially arranged burners 7, a turbine 8and an exhaust gas casing 9 succeed one another along the rotor 3.

In the compressor 5, an annular compressor duct 10 is provided, whichnarrows in cross section in the direction of the annular combustionchamber 6. At the outlet, on the combustion chamber side, of thecompressor 5, a diffuser 11 is arranged, which is flow-connected to theannular combustion chamber 6. The annular combustion chamber 6 forms acombustion space 12 for a mixture consisting of a fuel and of compressedair. A hot-gas duct 13 is flow-connected to the combustion space 12, thehot-gas duct 13 being followed by the exhaust gas casing 9.

Blade rings are in each case arranged alternately in the compressor duct10 and in the hot-gas duct 13. A guide blade ring 15 formed from guideblades 14 is followed in each case by a moving blade ring 17 formed frommoving blades 16. The fixed guide blades 14 are in this case connectedto a guide blade carrier 18, whereas the moving blades 16 are connectedto the rotor 3 by means of a disk 19.

The guide blades 14 are fastened to the guide blade carrier 18 and attheir end facing the guide blade carrier 18 have platforms 21 whichoutwardly delimit the hot-gas duct 13. Arranged adjacently to theplatforms 21 of the guide blades 14 in the flow direction are guiderings 22 which lie opposite the tips of the moving blades 16 and whichdelimit the hot-gas duct 13. The platforms 21 of the individual guideblades 14 of a guide blade ring 15 in this case form a ring 25 which isadjacent to the guide ring 22 consisting of segments and between whichan annular gap 23 is enclosed. The guide ring 22 and the platform ringin this case form an inner casing 37 for the working fluid 20 flowingthrough the rings.

While the gas turbine 1 is in operation, air 21 is sucked in by thecompressor 5 through the intake casing 4 and is compressed in thecompressor duct 10. Air L provided at the burner-side end of thecompressor 5 is led through the diffuser 11 to the burners 7 and ismixed there with a fuel. The mixture is then burnt in the combustionspace 10 so as to form a working fluid 20. The working fluid 20 flowsfrom there into the hot-gas duct 13. At the guide blades 14 arranged inthe turbine 8 and at the moving blades 16, the working fluid 20 expandsso as to transmit pulses, so that the rotor 3 is driven and, with it, aworking machine (not illustrated) coupled to it.

FIG. 1 shows a detail of the gas turbine 1 with a gap, for example anannular gap 23. The annular gap 23 is in this case formed between afirst component, the platform 21 of the guide blade 14, and a secondcomponent, the guide ring 22. FIG. 1 illustrates only the componentsessential to the invention, that is to say the illustration of guideblades 14 and moving blades 16 and of the fastening of the guide ring 22and of the platform 21 is dispensed with.

As seen in the flow direction of the working fluid 20, the platforms 21form the front ring 25 and the guide ring 22 forms the rear ring 26. Thefront ring 25 has integrally formed on it, radially on the inside, afirst collar 27 which extends in the direction of the following rearring 26 along the conical run of the hot-gas duct 13. The rear ring 26has integrally formed on it, radially on the outside, a further collar28 which overlaps the first collar 27, as seen radially from the insideoutward, so that the annular gap 23 is formed in cross section as anoverlap gap. An overlap gap, in which the radially outer collar 28 isarranged on the front ring 25 and the inner collar 27 is arranged on therear ring 26, would, of course, also be possible.

Along the annular gap 23, as seen from the inside outward, the latterfirst has a gap portion which runs in the radial direction and which isdeflected in a bend 38 by the outer collar 28, so that said gap portionhas adjoining it in the axial direction a gap portion 29 which extendscounter to the flow direction of the working fluid 20. A second bendthen occurs, which deflects the annular gap 23 into the radial directionagain.

An annular bearing surface 32 is arranged on that side of the firstcollar 27 which faces away from the working fluid 20. The annularsupporting surface 33 is located, opposite the annular bearing surface32, on the outer collar 28.

A groove, preferably a circumferential groove 31, is provided in thatend face 30 of the rear ring 26 which faces the front ring 25.

The first end 34 of the spring element 24 is crimped and inserted intothe circumferential groove 31. In this case, the circumferential groove31 may be somewhat smaller in its width than double the materialthickness of the spring element 24, in order to achieve an effectivelybearing and reliable connection to the rear ring 26. The spring element24 may likewise be soldered or welded in the circumferential groove 31to the rear ring 26.

The first end 34 of the spring element 24 has adjoining it, in crosssection, a spring region which runs in a slightly convex arc and whichis supported on the annular supporting surface 33. A prestress in thespring element 34 is thereby generated which is directed in thedirection of the annular bearing surface 32.

The convex arc, that is to say the spring region of the spring element24, has adjoining it a free second end 35 formed by a concave arc 39. Inorder to achieve a good displaceability of the second end 35 on theannular bearing surface 32, the concave arc 39 of the spring element 24bears, air-tight, against the annular bearing surface 32 along a contactline 40 directed in the circumferential direction.

A rear space 36 separated from the hot-gas duct 13 by the rings 25, 26is separated, air-tight, from the hot-gas duct 13 by means of the springelement 24 which bears against the two rings 25, 26 and is likewisedesigned as a ring consisting of segments.

In order to cool the rings 25, 26 or ring segments acted upon by the hotworking fluid 20, in the rear space 36 a cooling fluid flows, thepressure of which is higher than that of the working fluid 20. Theprestress of the spring element 24 is assisted by the force generated bythe pressure drop, so that the spring element 24 is pressed even morefirmly against the annular bearing surface 32. A low cooling fluidoutflow as a result of positional deviations, not to be ruled out,between individual segments of a ring or as a result of a surfaceroughness of the annular bearing surface 32 serves for cooling thespring element 24.

The spring element 24 may in this case be produced from a heat-resistantalloy, for example from an alloy bearing the tradename of Nimonic 90.

FIG. 3 shows the two rings 25, 26 in a position displaced in relation toone another after thermal expansion has taken place. In respect of FIG.1, the length of the gap portion 29 is shortened, as seen in the flowdirection of the working fluid 20, but the distance between the twocollars 27, 28 or the distance of the annular bearing surface 32 fromthe annular supporting surface 33 has increased, as compared withFIG. 1. As regards the rotor 3, the two rings 25, 26 forming the annulargap 23 are displaced in relation to one another both in the radialdirection and in the axial direction.

Alternatively to FIG. 3, FIG. 4 shows a spring element 24 clamped in themanner of a joint as a result of the calking of the circumferentialgroove 31, so that there is a slight movability of the spring element 24in the manner of a hinge.

By virtue of the spring prestress, the free end 35 of the spring element24 remains in contact with the annular bearing surface 32 in spite ofthe high displacement travel and thus seals off the rear space 36 withrespect to the hot-gas path 13. Slight leakage streams of cooling fluidthrough the annular gap 23 into the hot-gas duct are in this casepossible, and, as compared with the prior art, an improvement in thesealing action and a reduction in leakage are furthermore achieved.

Owing to the annular arrangement of the platforms 21 and guide rings 22and due to the radial mounting required for these components, theplatforms 21 described in the description and claims, the guide bladerings 15, the rings 22, 25, 26 and also the spring elements 24 are ineach case to be understood as meaning only segments of the respectivering.

Furthermore, the sealing means proposed may be used both betweenadjacent platforms of an individual blade ring and in other regions ofthe gas turbine, for example in the combustion chamber, when an overlapgap is formed between the components to be sealed off.

1. A gas turbine engine, comprising: a rotationally mounted rotor havinga longitudinal axis; an axial compressor arranged coaxially along therotor that produces a compressed intake fluid flow; a combustion chamberarranged downstream of the compressor which receives the fluid flow anda fuel, and combusts the fluid flow and the fuel to form a hot workingmedium flow; a turbine that receives and extracts mechanical energy fromthe hot working medium flow; a rotationally fixed inner casing whereinthe hot working medium flows through a passage within the inner casing,the inner casing comprising: a front ring having a collar portionextending in the axial direction arranged coaxially with the rotor, anda rear ring having a collar portion extending in the axial directionarranged coaxially and down stream of the front ring with respect to thedirection of flow of the working medium, the front and rear ringsforming an annular gap in an area where the collars partially overlap,and a single element spring arranged to seal the annular gap from thehot working medium having a first end, a radially free second end and aspring region arranged between the first and second ends, the first endsecured in a circumferential groove of either the front ring or the rearring and the second end in intimate contact with a bearing surface ofthe collar of the other inner casing ring sealing the annular gap fromthe hot working medium such that the second end accommodates both radialand axial relative motions between the front and rear rings, wherein awidth of the circumferential groove is smaller than a width of thespring element first end to provide a secure and sole retention of thespring element in the circumferential groove due to an interferencebetween the spring element first end and the circumferential groove. 2.The engine as claimed in claim 1, wherein the inner casing divergesconically toward the rotor in the direction of flow.
 3. The engine asclaimed in claim 1, wherein the front ring has a radially inner collarand the rear ring has a radially outer collar.
 4. The engine as claimedin claim 3, wherein the front ring forms the radially outer collar andthe rear ring forms the radially inner collar such that the annular gapextends in the direction of flow of the working fluid.
 5. The engine asclaimed in claim 1, wherein the radial width of the circumferentialgroove is less than twice the material thickness of the spring seal. 6.The engine as claimed in claim 5, wherein the first end of the springelement is connected to the circumferential groove by welding orsoldering.
 7. The engine as claimed in claim 1, wherein an annularbearing surface is provided on the radially inner collar on a sideopposite the working medium.
 8. The engine as claimed in claim 1,wherein the spring seal element has a S-shaped cross section.
 9. Theengine as claimed in claim 1, wherein a cooling medium exerts a higherpressure on an outer diameter surface of the spring seal elementrelative to the pressure exerted on the inner diameter side by the hotworking medium.
 10. A gas turbine hot gas sealing system comprising: afirst component having a collar portion; a second component having acollar portion adjacent the first component collar portion, the firstand second collar portions partially overlapping to form an annular gap,the second component having a circumferential groove open to the annulargap; and an annular single element spring seal arranged to seal theannular gap from a hot gas in the turbine having a first end, a radiallyfree second end and a spring region arranged between the first andsecond ends, the first end region secured within the circumferentialgroove and the second end in direct contact with the collar of the firstinner casing ring sealing the annular gap from the hot gas such that thesecond end accommodates both radial and axial relative motions betweenthe first and second components, wherein a width of the circumferentialgroove is smaller than a width of the spring seal element first end toprovide a secure and sole retention of the spring seal element in thecircumferential groove once the spring element first end is insertedinto the circumferential groove due to an interference between thespring element first end and the circumferential groove.
 11. The sealingsystem as claimed in claim 10, wherein the circumferential groove isfacing the annular gap.
 12. The sealing system as claimed in claim 10,wherein the first end of the spring element is welded or soldered to thecircumferential groove.
 13. The sealing system as claimed in claim 10,wherein the spring element has an S-shaped cross section.
 14. Acompliant turbine hot gas seal system, comprising: a first hot gascomponent having an annular surface concentric with a centerline of theturbine; a second hot gas component having a recessed surface arrangedproximal and concentric to the annular surface of the first componentdefining a hot gas gap between the first and second components; and asingle element seal component having a first, a radially free second anda third portion, the first portion arranged within the recess, theradially free second portion in sliding contact with the annular surfaceand the third portion arranged between the first and second portionswhere the third portion is a spring section and where the second portionaccommodates both radial and axial relative motions between the firstand second hot gas components, wherein the seal component ispre-stressed in the radial direction and exerts a contact pressureagainst the annular surface to prevent a flow of hot gas through the hotgas gap, wherein a width of the recess is smaller than a width of theseal component first portion to provide a secure and sole retention ofthe seal component in the recess once the seal component first end isinserted into the recess due to an interference between the sealcomponent first end and the recess.
 15. The seal system as claimed inclaim 14, wherein the first portion is welded or soldered to the secondcomponent.
 16. The seal system as claimed in claim 14, wherein the sealcomponent is S-shaped.
 17. The seal system as claimed in claim 14,wherein the seal accommodates radial and axial relative motion betweenthe first and second components.